Herbs with tuber or rhizome, paradioecious (sex depending on nutrition and therefore variable from one year to another). Tuber usually renewed seasonally and producing some tubercles around, these separated from old tuber at end of growth season. Rhizome usually cylindric, with many nodes, not renewed every year, usually preceding evergreen or wintergreen leaves. Roots usually growing at apex of tuber around cataphylls or at new nodes of rhizome. Cataphylls 3-5, herbaceous or membranous, surrounding basal part of shoot. Pseudostem consisting of basal cylindric part of petiole present or absent. Leaves 1-3, long petiolate; petiole usually mottled, stout, smooth or verrucose; leaf blade 3-foliolate, palmate, pedate, or radiate. Inflorescence borne with or before leaves, solitary, pedunculate, emerging from pseudostem in tuberous or some rhizomatous plants or separately from petiole and directly surrounded by cataphylls in some rhizomatous plants; peduncle (excluding part within pseudostem) erect, stout, usually shorter than or sometimes equaling or longer than petioles (excluding part forming pseudostem). Spathe tubular proximally, expanded limb distally, deciduous, withering or rarely semipersistent; throat of spathe tube often widely spreading outward, with or without an auricle on each side, margins of throat ciliate or not; spathe limb occasionally with a long tail at apex. Spadix sessile, unisexual or bisexual; bisexual spadix female proximally, male distally, neuter (sterile) flowers sometimes present on appendix; appendix variable in shape, base stipitate or not, apex sometimes ending in long filiform flagellum. Ovaries with 1 basal locule with several orthotropous ovules; style usually indistinct; stigma peltate, papillose. Synandria of 2-6 fused stamens, sessile or on a united filament; anthers dehiscing by 2 apical pores or a single horseshoe-shaped slit or circumscissile into a ring. Neuter flowers filiform, subulate. Infructescence upright or nodding. Berries reddish, several seeded.

About 180 species: NE Africa, Asia (including Arabian Peninsula), E North America and Mexico; 78 species (45 endemic) in 12 sections in China; one additional species (endemic) is incompletely known.

Many Chinese species of Arisaema are of medicinal importance. For example, the tuber of A. flavum is used to treat fractures, traumatic injuries, and swellings; the tuber of A. franchetianum is used to treat enlarged lymph nodes, intestinal parasites, and snake and insect bites; the tubers of A. erubescens, A. heterophyllum, and A. yunnanense are used to treat coughs, epilepsy, and tetanus. Many species of Arisaema have been found to possess anticancer properties.